Telephone system



H. W. BRYCE.

TELEPHONE SYSTEM.

APPLICATION fILED OCT-6,1915.

Patented Sept. 28, 1920.,

[EL/5277527 15 E127"; Z/Z/Br 5E. By

Z/Z/zTnessssx UNITED STATES HARRY W. BRYCE, OF DOWNERS GROVE,

BOARD AND SUEZ-LY COMPANY, NOIS.

ILLINOIS, ASSIGNOR TO KELLOGG SWITCH- Ol CHICAGO, ILLINOIS, A CORPORATION OF ILLL,

TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Sept. 28, 1920.

Application filed October 6, 1915. Serial No. 54293.

T 0 all whom it may concern.

Be it known that I, HARRY W. BRYCE, a citizen of the United and State of Illinois, have invented certain new and useful Improvements in Telephone Systems, of which the following is a specification.

My invention relates to telephone systems and has to ally operated link and trunk circuits which are employed for interconnecting telephone lines.

One of the features of my invention is the provision of a link circuit that is provided with so-called automatic ringing apparatus,

the operation of which is initiated by the insertion of the calling plug of the link circuit into the multiple jack of a called subscribers line and in which the said apparatus is rendered ineffective upon the insertion of the said calling plug into a trunk jack connected to a trunk circuit. Another feature of my invention is the novel means of controlling the calling supervisory signal of the link circuit when it is used in conjunction with a trunk circuit to extend a connection to a distant telephone exchange. Another feature of my invention is the novel means of controlling the supervisory apparatus of the trunk circuit and the novel of controlling the apparatus, associated with the outgoing end of the trunk circuit, fromth incoming end. These and other features will i be more particularly pointed out in the ensuing specification and the appended claims.

Referring to the accompanying drawing, the system there illustrated includes two substations A and B, which terminate in line circuits L and L at different exchanges. The cord circuit C which is at the same exchange with the line circuit of substation A is adapted for interconnecting lines terminating in its exchange or for extending connections to trunks leading to distant exchanges. The trunk circuit D, of which the outgoing end is located in the same exchange with the line of substation B, is connected to the trunk jack TJ in the exchange of sub station A. The line circuit L associated with the substation A comprises a double wound line relay LR, a cut-off relay CO, a line signal LS, and multiple jacks J, which States of America, residmg in Downers Grove, 1n Dupage county do more particularly with manusociated calling supervisory in practice, appear before different tors positions at the switchboard.

The operators cord circuit C includes an answering plug AP for connecting to calling subscribers lines and a calling plug GP operafor connecting to called subscribers lines or to trunk circuits terminating in distant exchanges. Associated with the answering plug AP is an answering tip supervisory relay AT and an answering sleeve supervisory relay AS, the latter relay operating to connect the operators telephone 0 with the calling subscribers line when the plug Ar is connected to a calling subscribers line. The relays AS and AT together control the calling supervisory lamp AL. Aswith the calling plug CP is a calling tip supervisory relay CT and a calling sleeve supervisory relay CS, the two relays cooperating to control the circuit of the lamp CL. I provide automatic ringing which is initiated upon connection of the calling plug GP to the jack of the called subscribers line, but which is rendered ineffective when the callplug CP is connected to a trunk jack TJ. l also provide a ringing control relay RC, an interrupter relay TR, and an interrupter I for controlling the automatic intermittent application of the ringing current from the generator G to the terminals of the called subscribers line. The operators control relay QC controls the disconnection of the operators telephone from the link circuit C.

The trunk circuit D terminates at the first exchange in a trunk jack T5 and at the distant exchange in the trunk calling plug TOP. The trunk jacks TJ may be multipled to a plurality of operators positions. Associated with the trunk jack TJ is the repeating coil R and the relays SC and SC, whose function will hereinafter appear. Associated with the incoming end of the trunk D at the distant exchange is a repeating coil R :1 double wound relay 2 provided with comparatively high resistance winding 8 and a comparatively low resistance winding 9, and a control relay CE for controlling the circuit of the supervisory lamp SL. Associated with the trunk calling plug TCP is the calling sleeve supervisory relay AS and a calling tip relay GT 1 provide aparty line ringing key BK for associating the desired ringing ourrent generator with the trunk circuit D for signaling the desired substation upon a trol relay RCR, an interrupter party line.

interrupter relay 1R for controlling and for intermittently providing ringing current from the desired generator to the called subscribers line. The line circuit L assoonly trunks of 13 B and B being shown) comprise a double wound cut-off relay CO aline. relay LE for contrtolling the line signal-LS and ia plurality ofjacks J Having described in general the apparatus used in -the system illustrated, the operation ofsaid system for connecting two subscribers in different exchanges and for connecting two subscribers in the same exchange, will now be described.

Assummg the subscriber at substation A ,desires connection with the subscriber at substation B, whose line terminates at a distant exchange, he first removes his receiver from its switch-hook thereby establishing a Y "circuit through the line relay LR; The line rela u on ener izin closes a circuit 7 through the line signal lamp LS to notify the operator that a connection is desired.

The operator in response to the said signal inserts the answering plug AP of the cord circuit G into the jack J, thereby establishing a serles energizing circuit for the cutoperator, upon learning that the subscriber at substation 13 1s desired, whose line terminates in a distant exchange, presses the 'orderwire key OK leading to the said exchange, in which the line of substation B terminates andinquires of the distant operator which trunk is to be used for the connection. The operator at the first exchange havingbeen assigned to the trunk D inserts the calling plug GP into the trunk jack TJ.

Responsive to the connection of the plug GP to the trunk jack TJ, a series circuit is closed through the supervisory control relay S0 and the calling sleeve relay CS and operators control relay O0 in multiple, traced from ground through the said relay SC}, sleeve contact ofthe trunk jack TJ and calling plug CP, and through the said calling-sleeve relay CS and control relay O0 to I also provide a ringing con- I and an battery. .The resistance of relay S0 is such that it does not permit suflicient current to flow through the relay CS to cause it to oper'ative'l energize. l-lowever, the relays SC and C energize in series, the former relay closing a circuit through the relay SC, associated with the trunk jack TJ, and through the high resistance winding 8 of the relay 2 associated with the repeating coil R the latter relay disconnecting the operators set from the strands of the link circuit C at its alternate contacts and 71.

The circuit for relay 2 may be traced from ground through the said high resistance winding 8 of relay 2, over a simplex circuit including: the windings 10 and 11 of the repeating coil R in multiple and windings 12 and 13 of the repeating coil R in multiple, alternate contact 14; of relay 8C and through the said relay SC to battery.

7 The resistance of the winding 8 of relay 2 is'such as to prevent a sufficient How of current to operatively energize relay SC. However, relay 2 energizes at this time and closes a circuit through the supervisory lamps SL and SL The circuit for supervisory lamp SL extends from ground through alternate contact'16 of relay 2, normal contact 17 of relay CR and through the said supervisory lamp SL to battery. The circuit for supervisory lamp SL extends from the same ground through alternate contact 16 of relay 2, normal contact 18 of relay CR, normal contact 37 of relay 35 and through the supervisory lamp SL to battery.

The operator at the distant exchange after receiving the number of the called subscriber from the subscribers operator, tests the line of-the called subscriber and assuming the said line to be idle she inserts the trunk calling plug TCP of the trunk circuit D into the jack J of the called subscribers line and presses a ringing button of key RK to select and connect the desired frequency to operate the call bell at thecalled subscribers substation. Upon the operation of the ringing button a circuit is closed through the ringing control relay ROB extending from ground through the contact of the operated button andthrough the said ringing control relay RCR to battery. The ringing control relay BUR, upon energizing, closes a locking circuit for itself,

traced from ground through alternate contact 16 of relay 2, normal contact 20 of relay AS, alternate contact 22 of said relay RCR and through its winding to battery. A further result due to the energization of the ringing control relay RUB is the closure ofa circuit through the calling tip relay GT traced from ground through the upper winding of the cut-oil relay CO the tip contacts of the jack J and trunkcalling plug TCP,- alternate contact 26 of relay ROR and through-the winding of said relay CT. to battery. The relay CO upon energizing, disconnects the line relay LR and 'connects the ring and sleeve conductors of the jack J 2 together at its alternate contact '29 of the repeating coil R and closes a circuit through relay CR to battery. The said relay CR, upon energizing, opens the circuit of lamp SL at its contact 17 and closes a substitute circuit for the supervisory lamp SL traced from ground through its alternate contact 18, normal contact 37 of relay 35, through the said lamp to battery. The circuit for the interrupter relay 1R which is closed upon the energization of the ringing control relay RCR, extends from ground through the lower winding of said relay, alternate contact 32 of relay RCR, through the interrupter I to battery. The interrupter relay upon energizing applies ringing current from the selected generator to the terminals of the called line, the path for the ringing current being traced from the selected generator through the ringing key contacts, alternate contact 33 of relay 2, alternate contact 34 of relay 1R sleeve conductor of the trunk calling plug TCP,

ring and sleeve conductors of the jack J through the called substation, back through the tip conductor of'jack J and plug TCP, alternate contact 25 of relay IR and through its non-inductive winding to battery.

Upon the response of the called subscriber at substation B, a circuit is closed through the answering sleeve supervisory relay AS traced from battery through the said relay, normal contact 34 of relay 1R sleeve contact of plug TCP, ring and sleeve contacts of jack J through the called subscribers substation and through the upper winding of relay CO to ground. The answering sleeve supervisory relay AS upon energizing, closes a circuit through relay 35, traced from battery through the said relay and through the alternate contact 36 of relay A53 to ground. The relay 35, upon energizing, closes a locking circuit for itself through its alternate contact 37 and also extinguishes the supervisory lamp SL thus notifying the trunk operator that the called subscriber has responded. A further result due to the energization of relay AS is the opening of the locking circuit for the ringing control relay RCR and the closing of a circuit through the winding 9 of relay 2 at its contact 20. The relay RCR, upon deenergizing, disconnects the interrupter I through the winding of said rela from the interrupter relay IR and opens the circuit of relay CT at its contact 26, the relay CT remaining energized, however, through its alternate contact 28. The closure of the circuit through winding 9 of relay 2 permits sufficient current to flow over the simplex circuit formed by the two conductors of the trunk circuit to permit relay SC, associated with the trunk jack TJ, to energize, the circuit extending from battery through the winding of said relay SC, alternate contact 14 of SC simplex circuit formed by the two trunk conductors, winding 9 of relay 2, alternate contact 20 of relay AS and alternate contact 16 of relay 2 to ground. Relay SC, upon energizing, closes its alternate contact 40 thereby closing a circuit for the calling tip supervisory relay CT of link circuit C through the impedance coil 1C the circuit extending from battery through the said coil 1C normal contact 41 of relay IR, ring contacts of plug CP and jack TJ, windlng 42 of repeating coil R, alternate contact 40 of relay SC, winding 38 of repeating coil R, tip contacts of jack TJ and plug CP, normal contact 44 of relay IR and through the calling tip supervisory relay CT to ground. The relay CT upon energizing, efl'aces the calling lamp CL, thus notifying the operator at the link circuit C that the called subscriber has responded and prepares a circuit for the guard relay GR. A further result due to the energization of relay SC is the closure of an operating circuit for calling sleeve supervisory relay CS, traced from battery through the said relay CS, sleeve contacts of plug CP and jack TJ, through the resistance X and alternate contact 45 of relay SC to ground. The resistance X is such as to permit the calling supervisory sleeve relay CS to receive sufiicient current to effectively energize. Relay CS, upon energizing, closes a circuit through the guard relay CTR traced from battery GR, nor mal contact 46 of ringing control relay RC,

alternate contact 47 of relay CT and through the alternate contact -18 i of relay CS to ground. The guard relay, upon energizing, closes a locking circuit for itself through its alternate contacts 19 and opens the circuit of relay RC at its contact 50. The subscril ers may now carry on an uninterrupted conversation over the heavily marked conductors.

Assuming now that the subscribers lave finished conversation, the subscriber at substation replaces his receiver upon its switch-hook opening the circuit of the unswering tip supervisory relay AT of the cord circuit C thus permitting the relay to again close its normal contact 51 to thereby cause the supervisory lamp AL to glow.

The subscriber at substation B, replacing tactscloses acircuit for supervisory lamp SL at itsIrormal=contact.37.- Belay SG upon de- -energizing,-:opens the-circuit of the calling tip supervisory relay GT at its. contact d0,

his receiver upon its switch-hook, opens the circuit of answering sleeve supervisory relay AS at the switch-hook contacts. The

relay A8 upon deenergizing, opensthe circuit or relay 35 at its contact 36, and opens the operatin circuit of relay SG atzits con- 20.- Pxelay 35 upon deenerglznig,

thereby permitting the'said relay to de'e'n- 'ergize and close a circuit-through'the calling lamp CL at its normal contact 47. The re-.

ring sleeve supervisoryrelay opening the series circuit of My G8, however, remains energized, it being so ad uSted that after it once operatlvely. energ1zes,--1t remalns so, due to thecurrentre ceived through the relay 8G The operator at the cord'circuit -G noting the two. lighted supervisory signals withdraws theplugs AP and GP from their respective-jacks J and TJ.' The removal of the plug-AP from its jack J permits the cutoff relay of line-circuit L to deenergi e-and the answering sleeve supervisory relay AS to deenergize.

The removal of the calling plug GP'from the jack TJ permits the call- GS and the operators control relay 0 to deenergize. The relay GS, upon deene'rgizing, permits the guard relay GR to deenergize thereby placing the link circuit C in condition to agaln be used to establish connectionv between subscribers lines. The removal of the calling plug GP from trunkjac'k TJ also permits the relay SG trunk c1rcu1t D in condition to be used for extending further calls.

Assuming now that the calling subscriber A wishes connection with a second subscriber located at the same exchange, the call proceeds as hereinbefore described upto the point where the operator inserts the calling plug into the trunk jack TI. In-this instance the operator inserts the calling plug GP into a multiple jack J (similar to-the jack J of the line circuit L) of the called subscribers line. The insertion of the calling plug GP into the jack of the calledsubscribers line closes an energizing circuit for the operators control relay 0G and the calling sleeve relay GS in multiple and through the cut-off relay of the called subscribers line. The operators control relay 0G, upon energizing, disconnects the operatorstelephone'froni the link circuit. The calling sleevesupervisoryrelay GS, upon energizing, closes a circuit through the calling supervisory lamp; CL and through ringing control relay BC, the latter circuit being traced*f-rom battery throiwh the winding of The relay IR, through the medium of the interrupter I, operates to intermittently connectringing-current from generator-Gr to the terminals of the called subscribers line.

Upon the response of the called subscriber, a series en'ergizingcircuit, including the calling'tip relay GT and the impedance coil 1C is closed.- The calling tip relay upon ener gizing, opens the circuit of the calling supervisory lamp GL and opens the circuit of the ringing control relay-RC. The ringing control-relay ,RG thereby'deenergizes and opens the'circuit of the interrupter relay IR at its contact 60. The two local subscribers may now carry on a. conversation over the heavily marked .conductors.

Assuming now that conversation has been terminated, the calling subscriber A, upon replacing his receiver,=causes the answering supervisory lamp ALto glow in the same manner as hereinbefore described. The called subscriber, upon replacing his receiver', opens thecircuit of the calling tip relay GT thereby. permitting the said relay to deenergizeand to close a circuit through the calling lamp GL. The operator, upon noting the glowing ofthe two supervisory lamps, rem oves the answering plug AP and calling plugfGP from'their respective jacks thereby permitting the apparatus to return to normal.

- While I have described my invention opcrating in connection with a' certain circuit arrangement, I do not wish to be limited to the'same, as my invention can be adapted to operate in conjunction with other circuit arrangements and m'any changes and modifications will readily suggest themselves to those skilled in the art. Therefore, I do not wish to be limited to the exact structure shown, bu't aim to cover all such changes and modifications as come within the spirit and scope of the appended claims.

Having described my invention, what I claim as new anddesire to secure by United States Letters Patent, is:

1. In a telephone system, amanual link circuit provided with automatic signaling apparatus, a relay associated with said link circuit for initiating-the operation of said signaling apparatus, a called subscribers line circuit, a trunk circuit, and means effective upon connection of said link circuit to said line circuit for operatively energizing said relay to initiate the operation of said signaling apparatus, said relay being ineffective upon the connection of said link circuit to said trunk circuit to operate said signaling apparatus.

2. In a telephone system, a manual link circuit provided with automatic signaling apparatus, a relay associated with said link circuit for initiating the operation of said signaling apparatus, a called subscribers line circuit, a trunk circuit, means effective upon connection of said link circuit to said line circuit for operatively energizing said relay to initiate the operation of said signaL ing apparatus, said relay being inefiect've upon the connection of said link circuit to said trunk circuit to operate said signaling apparatus, and a supervisory circuit controlled by said relay.

3. In a telephone system, a manual link circuit provided with automatic signaling apparatus, a relay associated with said link circuit for initiating the operation of said signaling apparatus, a called subscribers line circuit, a trunk circuit, means effective upon connection of said link circuit to said line circuit for operatively energizing said relay to initiate the operation of said signaling apparatus said relay remaining inert upon the connection of said link circuit to said trunk circuit thereby preventing the operation of said signaling apparatus, and means associated with said trunk circuit for thereafter operating the said relay for controlling a supervisory circuit without atfecting the said ringing apparatus.

4. In a telephone system, a manual link circuit provided with automatic signaling apparatus, a relay associated with said link circuit for initiating the operation of said signaling apparatus, a called subscribers line circuit, a trunk circuit, means effective upon connection of said link circuit to said line circuit for operatively energizing said relay to initiate the operation of said signaling apparatus, said relay remaining inert upon the connections of said link circuit to said trunk circuit thereby preventing the-operation of said signaling apparatus, and means associated with said trunk circuit for rendering said automatic ringing apparatus ineffective and for operating said relay for controlling the supervisory circuit.

5. In a telephone .system, a manual link circuit provided with a calling supervisory si al, a relay connected to a talking strand of gaid link circuit for controlling said signal', a trunk circuit for connection to said link circuit for extending connection to. a distant exchange, a'called subscribers line circuit adapted to be connected to said trunk circuit, and means controlled by said called subscriber over the two sides of the said trunk circuit in multiple for actuating said relay to cause an operation of said supervisory signal.

6. In a telephone system, a manual link circuit provided with a calling supervisory signal, a relay connected to a talking conductor of said link circuit, a. trunk circuit connected to said link circuit for extending a connection to a distant exchange, a called subscribers line circuit connected to said trunk circuit, and means controlled by the called subscriber over the two sides of the said trunk circuit in parallel for operating said relay for controlling said supervisory circuit.

7. In a telephone system, a manual link circuit provided with a calling supervisory signal, a relay connected to a talking conductor of said link circuit, a trunk circuit connected to said link circuit for extending connections, a called subscribers line circuit connected to said trunk circuit, and a simplex circuit including the two conductors of said trunk circuit for controlling a trunk circuit relay, means controlled by said trunk circuit relay for uniting the conductors of said link circuit thereby operating said first relay and actuating said signal, said simplex circuit being controlled by the calledsubscriber.

8. In a telephone system, a manual link circuit provided with a pair of talking conductors, a supervisory relay connected to one of said talking conductors, a trunk circuit connected tosaid link circuit, a called subscribers line circuit connected to said trunk circuit, a simplex circuit including the two conductors of the said trunk circuit, means controlled by the called subscriber for increasing the current flowing in said simplex circuit, and means controlled by such increased flow for closing a bridge across said talking conductors to operate said supervisory relay.

9. In a telephone system the combination of a manual link circuit and a trunk circuit for extending connections between subscribers lines, a pair of supervisory signals for said trunk circuit, means'controlled by the connection of said link circuit to said trunk circuit for causing said supervisory signals to glow, means controlled by the connection of said trunk circuit to the called subscribers line for effacing one of said signals, means controlled by the response of a called subscriber for effacing the other of said signals, means controlled by the disconnection of said trunk circuit from said called .subscribers line for again causing said first supervisory signal to glow, and means controlled by the disconnection of said link circuit from said trunk circuit for again efi'acing said last signal.

10. In a telephone system the combination of a manual link circuit and a trunk circuit for extending connections between subscribers lines, a pair of supervisory signals for said trunk circuit, means controlled by the connection of said link circuit to said trunk circuit for causing said supervisory signals to glow, means controlled by the connection of said trunk circuit to the called subscribers line forerfacing one ofsaid signals, means controlled by the response of a called subscriber ior effacing the other of said signals, and means controlled by the disconnection of said trunk circuit from said called subscribers line for again causing said first supervisory signal to glow.

11. In a telephone system the combination of a link circuit connected to a trunk circuit, of acalled subscribers line circuit connected to said trunk circuit, a pair of supervisory signalsfor said trunk circuit operative upon connection-of said link circuit to said trunk circuit, means tor eilacing one off saidsignals upon the connectionv of said trunk cir cuit to the called subscribers line, means controlled by the called subscriber for effacing the other of said signals, means for again causingsai'd signals torglow, and operator and subscriber controlled means for again eflacing said signals.

12. In a telephone system, a manual link circuit, a trunk circuit provide'dwith a pair of supervisory signals, means responsive 'to the connection of saidlink circuit to said trunk circuit to cause said signals to glow, subscriber controlled means for effacing one oi'jsaid :signals, and operator controlled means for 'efiacingtheother of'said signals.

13. Ina. telephone system, .a manual link Gimme provided with automatic signaling apparatus, subscribers line circuit,.a trunk circuit for extending connections, meansresponsive tothe; connection of said manual link, circuit to; said.. subscribers line circuit for. rendering salt signaling apparatus effective to signal the called substation, and

means associated. with. said trunk circuit for preventing the operation of said automatic signaling apparatus when connection is, establishedbetweensaid link circuit and said trunlrcircuit. V V p 14 In a telephone system, aymannal link circuit provided with automatic signaling 7 apparatus, a called subscribers line circuit,

a-trunk circuit extending tov a distant exchange, means respons ve to the vconnection of said manual link circuit to, said fsubscrib- V QTSLljlfllG circuitfor initiatingthe operation of said automatic signaling apparatus, and

apparatus associated, with-said trunk circuit r mi e eme l al na paratus, ineffective- 15([In a telephone system,la. m anual link 7 a circuit provided with,automatic signaling apparatus, a called subscribers line, a trunk circuit, and electromagnetic means for said link circuit operative to actuate said ringing apparatus when the link circuit is connected to said called subscribers line and for rendering inefi'ective said ringing appa-, ratus when said link circuit is connected to said trunk circuit. 7

16."In a telephone system, a two-conductor link circuit, a supervisory relay connected to said link circuit, a trunk circuit, manual means for connecting said'link circuit to said trunk circuit, apparatus associated with said trunk circuitand controllable over the two conductors thereof in parallel to unite said link circuit conductors toactuate said supervisory relay.

17. In a telephone system, a manual link circuit provided with automatic signaling apparatus, a called subscribers line, .a' trunk circuit, electromagnetic means for said link circuit operative to actuate said ringingappa'ratus when the link circuit is connected to said called subscribers linefand for rendering ineffective said ringing apparatus when said link circuit is connected to said trunk circuit, and a supervisory signal for said link circuit operable either over said called line or over said trunk circuit.

18. In a telephone system, a two-conductor link circuit, a supervisory relay connected to said link circuit, a trunk circuit,

connected to said trunk circuit, avpai'r-of supervisory signals for said trunkrcircuit,

means controlled by the connection of said linkcircuit to said trunk circuitior operating said supervisory signals, means responsive to the connection of said trunk circuit to said called subscribers line circuit to efi'ace one of said signals, and means, responsive to i the response of the called subscriber for efiacingthe'other ofsaidsignals.

20. In a telephone system, afsub'scrib'ers line, a link circuit, atrunkcircuit, a pair of signals for said trunk circuit,;means responsive to the connection of. said link circuit to said trunk circuit to operate said signals,

means responsive to the connection of said trunk circuit .to said subscribers line to effaceone of said signals, .andsubscriber controlled means, tor efiacing the other of said signals, I

21. In a .telephoneisystem, .a .,subscribers line, alink circuit, a trunk circuit, supervisory signals for said trunk circuit, circuits iso ' for said supervisory signals closed responsive to the connection of said link circuit to said trunk circuit, means for opening one of said circuits responsive to connection of said trunk circuit to said subscribers line, means controlled by said subscriber to open and close the other of said circuits, and means controlled by the disconnection of said link circuit from said trunk circuit to again close said first circuit.

22. In a telephone system, a subscribers line circuit, a link circuit, a trunk circuit, a supervisory signal for said link circuit, means controlled over said line circuit when said link circuit is connected directly to said line circuit to operate said signal, and means controlled over the two sides of the trunk circuit in parallel to operate said signal When said link circuit is connected to said trunk circuit.

23. A telephone system including a manual link circuit provided with a pair of talking conductors, a calling line connected to said link circuit, a calling supervisory signal, a relay connected to one of said talking conductors for controlling said signal, a trunk circuit, manual means for connecting said trunk circuit to said link circuit to extend a connection therefrom, a called subseribers line connected to the opposite end of said trunk circuit, a simplex circuit ineluding said trunk circuit, means for producing a change in said simplex circuit to operate said link circuit relay to thereby actuate said signal, and central otllce means for supplying both said calling line and said called line with talking current.

24. A telephone system including a manual link circuit provided with ringing means, a called subscribers line, a trunk circuit, means responsive to the connection of said link circuit to said called subscribers line to actuate said ringing means, and means associated with said trunk circuit to prevent the operation of said ringing means when said link circuit is connected to said trunk circuit.

25. A telephone system including a manual link circuit, ringing means associated with said link circuit, a subscribers line circuit, a trunk circuit, and means for said link circuit operative only when said link circuit is connected to said subscribers line for initiating the operation of said ringing means.

Signed by me at Chicago, in the county of Cook and State of Illinois, in the presence of two witnesses.

HARRY W. BRYCE. Witnesses:

G. A. YANOCHOWSKI, B. OBRIEN. 

